1. Field of the Invention
The present invention relates, in general, to a method and system for controlling a hybrid electric vehicle, and more particularly, to a method and system for controlling a hybrid electric vehicle which, when failure has occurred in an EOP temperature sensor and torque to be applied to a transmission is controlled to protect the transmission, can actively control the range of torque to be applied to the transmission according to a gear shift state, instead of controlling the range of torque to be applied to the transmission at a predetermined level, by comparing the density of phase currents with the density of coil phase currents acquired when currents which do not cause a coil to burn.
2. Description of the Related Art
First, for better understanding of the present invention, a general hybrid electric vehicle will be schematically described as follows:
A hybrid electric vehicle is a vehicle which uses an engine and a motor as driving sources, and is capable of reducing exhaust gas and improving fuel efficiency. The hybrid electric vehicle includes an engine and a drive motor configured to function as driving sources for the vehicle, an engine clutch interposed between the engine and the drive motor, a transmission connected to the output side of the drive motor and configured to transmit power to a drive shaft, a battery configured to function as a power source (electric power source) for the drive motor, and an inverter configured to control the drive of the drive motor.
The hybrid electric vehicle is mounted with a Hybrid Control Unit (HCU) for generally controlling the vehicle and other various control units for controlling the respective devices of the vehicle.
For example, the hybrid electric vehicle includes an Engine Control Unit (ECU) for controlling the operation of the engine, a Motor Control Unit (MCU) for controlling the operation of the drive motor, a Transmission Control Unit (TCU) for controlling the operation of the transmission, a Battery Management System (BMS) for controlling the operation of the battery while monitoring the state of the battery, and a Full Auto Temperature Controller (FATC) for controlling the indoor temperature of the vehicle.
Further, the HCU, which is the highest-level control unit, performs cooperative control with the control units, such as the ECU, the MCU, the TCU, the BMS, and the FATC for controlling the respective devices by transmitting and receiving information with each other through Controller Area Network (CAN) communication. High-level control units transmit commands, such as a control signal, to lower-level control units while collecting various information from the lower control units.
The hybrid electric vehicle further includes an Electric Oil Pump (EOP) for supplying working fluids required for driving the engine clutch and the transmission, and an Oil Pump Unit (OPU) including a pump control unit for controlling the operation of the EOP and a relay for controlling the supply of electric power to the EOP.
The pump control unit of the OPU is provided to transmit and receive information to and from the TCU which is the high-level control unit through the CAN communication, and is configured to electrically control the operation of the EOP based on a control signal applied from the TCU.
The EOP includes a motor and a pump in general, and drives the pump using the power of the motor.
The OPU performs a function of driving the EOP by controlling the supply of electric power to the EOP as described above. When the EOP is overloaded, the OPU performs a function of controlling the torque of the EOP by raising the value of phase currents such that the EOP can spin after coping with the overloads.
An EOP temperature sensor measures the temperature of the most heated coil inside the motor, and the OPU constructs a regular protection logic using a Phase Current Sensor (CS) in order to protect an internal power module.
In particular, a coil may be burning under a high load condition because the coil is rapidly heated and the temperature of the coil deviates from temperature at which the coil can stand. Conventionally, a coil is prevented from being burning in such a way that the OPU continuously monitors the temperature of the coil and reduces the output of the EOP when the temperature of the coil reaches regular temperature before the temperature of the coil deviates from the temperature at which the coil can stand.
The EOP is mounted with a temperature sensor inside in order to prevent main elements from being burning because the motor is heated due to overcurrent, and is configured to perform a regular control logic function to protect the EOP or peripheral equipment using a signal received from the temperature sensor.
In a case of single EOP driving system, the torque to be applied to a transmission is limited to a regular value or less in order to protect the transmission when the temperature sensor is broken down.
In particular, since the torque to be applied to the transmission is uniformly limited to a regular value without taking a vehicle's traveling step (before and after shifting gear stages) into consideration, the range of the torque which can be applied to the transmission is limited when failure has occurred in the temperature sensor, and thus a problem occurs in that the total vehicle efficiency and shifting smoothness are decreased.
As related technology, a conventional art entitled “Device and Method for Controlling Oil Pump of Hybrid Electric Vehicle” and another conventional art entitled “Method for Driving Oil Pump for Hybrid Electric Vehicle” are disclosed. However, in a case of “Device and Method for Controlling Oil Pump of Hybrid Electric Vehicle”, power required to control an electric oil pump is determined based on oil temperature and change in line pressure according to the requested torque, and thus an advantage is realized in that the speed of revolution of the electric oil pump can be actively controlled. However, there is a limit in that it is difficult to actively control the torque to be applied to the transmission using the phase current sensor as in the present invention. In a case of the “Method for Driving Oil Pump for Hybrid Electric Vehicle”, it is possible to continuously drive a motor even when failure has occurred in a state in which the TCU is communicated with the OPU, and thus the durability of a device is improved. However, there is also a limit in that it is difficult to actively control the torque to be applied to the transmission using the phase current sensor as in the present invention.
The contents, described as related art, are only intended to provide an understanding of the background of the present invention, and should not be understood that the present invention corresponds to already-known related art by those skilled in the art.